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A lot of changes were made to input data types and formats. As a result, your existing workflow might not work out of the box. Here you can find a list of the most important changes, why they were made and how to get started with BASEmesh v2.
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While care was taken to keep as much of the existing workflow for BASEmesh v2, the design changes performed did result in some alterations of the end user workflow.
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If you want to skip the details, you can jump straight to the [FAQ](#faq).
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## Missing features
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A number of features have not made it into this release of BASEmesh v2. Here is a brief overview of any v1 features that are not yet available in BASEmesh v2:
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| Tool | Feature | Note |
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|:-----------------:|:---------------------|:-----------------------------------------------------------------|
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| Elevation meshing | Custom mesh domain | Stability and performance concerns when trimming large data sets |
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| Quality meshing | Custom mesh domain | Stability and performance concerns when trimming large data sets |
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To skip the details, you can jump directly to the FAQ [here](#faq).
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## Elevation meshing
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### Input data
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The elevation meshing utility now prefers 3D lines as its primary input data. Auxiliary elevation points are still available, but mostly serve to "pad out" the areas in-between the break lines. For simple use-cases, the input line segments should be sufficient.
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The elevation meshing utility now exclusively uses 3D input geometries, preferably 3D lines. Auxiliary elevation points are still available, but mostly serve to help constrain the resulting triangulation in-between break lines.
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Layers containing 2D geometries will not be displayed in the drop-down menus.
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**Important:** Layers containing 2D geometries will not be displayed in the drop-down menus.
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If you want to convert your 2D input data to 3D, you can use the '*Convert legacy layer (Point)*' and '*Convert legacy layer (Line)*' algorithms in the QGIS 3 processing toolbox.
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### Mesh domain / boundary
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The mesh boundary has been done away with as it was a great source of problems when interpolating. The polygon was mostly a visual aid, internally it was converted to an outline and merged with the existing line segments.
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The mesh boundary has been done away with as it was a great source of issues when interpolating. The polygon was mostly a visual aid, internally it was converted to an outline and merged with the existing line segments.
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It was replaced by two different options: *'Keep convex hull'* and *'Shrink to segments'*.
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If you only intend to use a single elevation source for mesh interpolation (more on that later), you can use the '*Keep convex hull*' option. This will create a number of unneeded boundary triangles, but it does not require any additional inputs layers or work. Additionally, this allows the generation of elevation meshes using only point data.
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*'Keep convex hull'* allows the generation of elevation meshes from point data such as heavily thinned-out point clouds. If your project only requries a single elevation mesh for mesh interpolation (see [Mesh interpolation](#mesh-interpolation) for details on using multiple meshes), it is generally safe to use this option for most simple projects.
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To get a concave elevation mesh, add the boundary outline to your input line segments layer.
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> **Note:** During testing, some issues with the convex hull option were encountered with meshes that had collinear line segments at the mesh boundary. If you are experiencing issues, try the *'Shrink to segments'* option instead.
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> **Note:** There will be a new version of the mesh boundary polygon in the future. This version will not be required to match any existing geometries and will be used to trim the input data.
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>
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> Due to stability and performance issues, this feature has been deferred for the time being.
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For concave elevation mesh, the *'Shrink to segments'* is provided. This works similarly to *'Keep convex hull'*, but deletes any mesh elements that lie outside a closed, line-bounded segment. A hole in the exterior break lines can cause the entire mesh to be consumed as part of this operation.
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## Quality meshing
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... | ... | @@ -61,6 +52,14 @@ During interpolation, each mesh node is processed to determine its new elevation |
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If it succeeds at providing elevation at this point, it will return a valid elevation, which is then applied to the node. If it fails, the process is repeated with the next elevation source in the list. This is repeated until either an elevation source returns a valid elevation, or until the list of elevation sources is exhausted.
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### Output format
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The BASEmesh 2 interpolation utility supports two different modes of interpolation depending on the target version of BASEMENT.
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For BASEMENT v2.8, the mesh node interpolation is performed similarly to the previous versions of BASEmesh. BASEMENT v3.x instead assigns elevation information to the mesh elements, which are interpolated separately.
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The utility does allow interpolation of both the mesh nodes and the mesh elements. This creates a mesh compatible with both versions of BASEMENT, but also takes roughly twice as long to interpolate.
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## FAQ
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### What happened to mesh boundaries?
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